State and local fire investigators have not determined what caused the massive blaze that gutted a North Grosvenordale auto body shop Wednesday night, but they said it is not suspicious.

Fire crews from 13 departments and three states responded to the report of a fire at K&R Auto at 549 Riverside Drive at approximately 7:12 p.m. Though most of the blaze was extinguished in less than two hours, firefighters continued dousing hot spots until past 1 a.m. Thursday, Thompson Fire Marshal Rick Hayes said.

“It was a very hot fire with a lot of fuel,” Hayes said. “There were several barrels of lubricants and oil in the bay area which produced intense smoke.”

Those fuel barrels likely account for the explosions several neighbors reported hearing earlier in the evening, Hayes said. The fire forced the shut-down of several nearby streets and left a odor of burnt rubber, which lingered in the area Thursday morning.

Michelle Metivier and Rita Blais said they heard what sounded like a “piece of equipment hitting something” shortly after 7 p.m. Wednesday at their residence, a few feet from the auto shop. Within minutes, a firefighter ushered them across the street as the fire gained strength.

“Flames were shooting 20, 30 feet in the air,” Metivier said.

Blais described the owners of the shop as the “nicest people you ever met.” She said they regularly plow her driveway when it snows. She also praised the quick response of firefighters who halted the blaze before it could damage her home.

“They did a phenomenal job,” Blais said. “(The fire) was just feet away from us and they did a fantastic job.”

The shop is listed under Riverside Drive LLC, with Richard Desrochers named as the principal owner, according to local and state records.

The owners were not available for comment Thursday and there was no information on the future of the business.

Hayes said three structures at the property were involved in the fire, with the rear garage area sustaining the most damage. He said about half of that building had collapsed. Two other buildings received fire, water and smoke damage. Hayes said the sheer power of the fire made pinpointing an exact origin of the blaze challenging.

Departments that sent firefighters and equipment to the scene included Community, East Thompson, West Thompson, Thompson Hill, Quinebaug, Muddy Brook, Woodstock, Attawaugan, East Putnam and the Bungay Fire Brigade in Connecticut, West Glocester in Rhode Island, a Webster, Mass., tanker and FAST team, and a Dudley, Mass., fire truck.